What are cathodes and anodes?

Both are electrodes, which are conductors that allow electricity to flow into or out of a non-metallic part of a circuit (like an electrolyte in a battery).

Basic difference between a cathode and an anode?

The cathode is the electrode where reduction (gain of electrons) occurs. It attracts cations (positively charged ions). The anode is the electrode where oxidation (loss of electrons) occurs. It attracts anions (negatively charged ions).

Cathode and Anode: In Electrochemical and Electrolytic System

Cathode and Anode: These terms are widely used in electrolysis and electrochemical systems. Understanding them is important, as their charges vary based on the system and reaction they are involved in. Check out this complete article to clearly understand cathode and anode charges, symbols, roles, and examples.

ByAtul Rawal

Jul 16, 2024, 16:57 IST

Cathode and anode charges, symbols, roles, and examples.

What are Cathode and Anode? The cathode and anode are essential components of electrochemical and electrolytic systems. They play crucial roles in facilitating various chemical reactions by allowing the transfer of electrons through oxidation and reduction. Understanding their functions, differences, and reactions is key to properly knowing about their role in different systems. Let us learn more about them one by one.

What is a Cathode?

The cathode is the electrode where reduction (gain of electrons) occurs. It attracts cations (positively charged ions) in both electrochemical and electrolytic cells.

Function in Electrochemical Systems: In galvanic or voltaic cells, the cathode is the positive electrode where the reduction reaction occurs. Electrons flow from the anode to the cathode through an external circuit, providing electrical energy.
Function in Electrolytic Systems: In electrolytic cells, the cathode is the negative electrode. It attracts cations from the electrolyte, which gain electrons (are reduced) to form neutral atoms or molecules.

For example; In a zinc-copper galvanic cell, the cathode reaction is:

Cu₂⁺+2e−→Cu(s)

What is an Anode?

The anode is the electrode where oxidation (loss of electrons) occurs. It attracts anions (negatively charged ions) in both electrochemical and electrolytic cells.

Function in Electrochemical Systems: In galvanic or voltaic cells, the anode is the negative electrode where the oxidation reaction takes place. Electrons are released and flow through the external circuit to the cathode.
Function in Electrolytic Systems: In electrolytic cells, the anode is the positive electrode. It attracts anions from the electrolyte, which lose electrons (are oxidized) to form neutral atoms or molecules.

For example; In a zinc-copper galvanic cell, the anode reaction is:

Zn(s)→Zn²⁺+2e⁻

Reactions at Cathode and Anode

Electrochemical Cell Example: In a Daniell cell (zinc-copper cell):

Cathode Reaction (Reduction):
Cu²⁺+2e⁻→Cu(s)
Anode Reaction (Oxidation):
Zn(s)→Zn²⁺+2e⁻

Image Source: doubtnut.com

Electrolytic Cell Example: In the electrolysis of water:

Cathode Reaction (Reduction):
2H₂O+2e⁻→H₂+2OH⁻
Anode Reaction (Oxidation):

2H₂O→O₂+4H⁺+4e⁻

Image Source: energy.gov

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Examples of Cathode and Anode in Real Life

Batteries: In a typical alkaline battery, the anode is made of zinc, and the cathode is made of manganese dioxide. The reactions at the electrodes allow the battery to generate electrical power.

Electroplating: During electroplating, a metal object to be plated serves as the cathode. Metal cations in the solution are reduced at the cathode, forming a thin metal coating.

Corrosion: In a corrosion cell, the metal surface where oxidation occurs acts as the anode, and the metal surface where reduction occurs acts as the cathode, leading to the deterioration of the metal.

Cathode and Anode Differences

This table summarises the whole article and will help you better understand the cathode and anode with examples;

Feature	Cathode	Anode
Reaction Type	Reduction (gain of electrons)	Oxidation (loss of electrons)
Charge in Electrochemical Cell	Positive	Negative
Charge in Electrolytic Cell	Negative	Positive
Attraction	Attracts cations (positive ions)	Attracts anions (negative ions)
Example Reaction	Cu²⁺+2e⁻→Cu(s)	Zn(s)→Zn²⁺+2e⁻

Understanding the roles of cathode and anode is an important topic in chemistry. These electrodes facilitate essential reactions in both electrochemical and electrolytic cells. By knowing their functions, reactions, and differences, we can better understand the principles behind batteries, electroplating, and many other applications in science.